Machine parts, such as aircraft engines and gear boxes in which components move relative to each other, are often lubricated with a lubricant oil to reduce wear. Over time, small wear particles break off from machine components and build up in the oil. These wear particles generally begin with sizes in the range of 1-10 microns, but, when abnormal wear begins, larger particles, in the range of 10 to 50 microns are generated. The particle population and size of the particles tends to increase over time until eventually, a machine failure can result.
To monitor the change in lubricant wear particles, samples of the oil may be withdrawn from the machine at scheduled times and sent to a laboratory for analysis. A variety of off-line methods exist for measuring properties of lubricating fluids. For example, the suspended particles may be separated from the oil sample (e.g., by using a rotary particle depositor) and then quantified. Another method involves placing the oil sample in a container and creating a magnetic flux field using a sensing electromagnetic coil. The distortion of the flux field caused by the particle burden is then noted as a numerical Particle Quantifying (PQ) value (see U.S. Pat. No. 5,404,100). However, each of these methods takes time to generate wear information. As a result, critical failures of machines may occur even when samples are sent regularly for testing.
There are currently known apparatuses and methods of detecting lubricating oil debris, both ferrous and non-ferrous. The apparatus and method taught in U.S. Pat. No. 8,522,604 uses a single microchannel and an inductive pulse sensor to detect and count all metallic debris based on the inductive Coulter counting principle. However, this apparatus and method of detecting debris has two faults—it cannot detect non-metallic debris and it lacks the ability to incorporate multiple channels for higher throughput of data collection. Wear particle detection apparatus would benefit from the ability to detect non-metallic debris because many modern machine parts have components that are made of a non-metallic material such as plastic. In this context, the art would also benefit from being able to discern between metallic and non-metallic wear particles. The art would also benefit from the ability to use a multiplexed and multichannel inductive sensor because this will allow for a higher throughput of micro scale debris particles. Therefore, there remains a need for an apparatus and method which permits in-situ testing of lubricants that can detect both metallic and non-metallic debris and which has the ability to incorporate a multiplexed and multichannel inductive sensor which will use only one set of detection electronics.